Thermoplastic films have gained wide acceptance in the packaging industry, and such films are commonly employed to package foods in both liquid and solid form. Many thin films composed of polymeric materials, however, are highly pervious to oxygen and other gases such as carbon dioxide. A pouch composed of polyethylene, for example, allows relatively rapid penetration of atmospheric oxygen and other gases into the interior thereof, in comparison to containers made of metal or glass.
In the packaging of many food products and other products which are sensitive to or reactive with oxygen, it would be desirable to provide a packaging or container material composed of a polymer with good gas barrier properties. The contamination of food products with oxygen after packaging often has many undesirable effects, including discoloration, deterioration and spoilage of the product, as well as significant loss in acceptable shelf storage life.
Heretofore, it has been generally accepted that the permeability of a given polymeric film is directly related to its thickness. Increasing the film thickness to reduce permeability to gases is not always feasible because of the higher cost and poor handling qualities of thick films.